US3750027A
Expired / Lapsed
US
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Surface wave frequency discriminators
Assignee: Texas Instruments Inc
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Filing: 1970-08-12
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Granted: 1973-07-31
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Expires: 1990-08-12
Abstract
Abstract Disclosed are apparatus for constructing a frequency discriminator utilizing surface wave devices. A plurality of interdigitated surface wave transducers are formed on a piezoelectric substrate along a common acoustic channel. The signal from the output transducers is rectified and then filtered to separate the r.f. component from the audio signal. A frequency discriminator having a preselected frequency response characteristic may be synthesized by constructing the individual interdigitated transducers to have the appropriate center frequency and number of pairs of electrodes.
Inventors
- 👤 C Hartmann
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 08:24
CPC Classifications
H; H03; H03D; H03D3/00; H03D3/02; H03D3/06; H03D3/16
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
256 words
A surface wave frequency discriminator for an F.M. receiver comprising: a. a piezoelectric substrate; b. a broadband bidirectional interdigitated input transducer having a center frequency of 10.7 MHZ disposed on said substrate, said input transducer having first and second terminals for receiving an input signal, one of said terminals connected to circuit ground; c. a first broadband interdigitated output transducer having a center frequency greater than 10.7 MHz disposed on said substrate adjacent one end of said input transducer, spaced apart from said input transducer along the path of propagation of the surface wave generated by said input transducer, said first output transducer having first and second terminals, one of which is connected to circuit ground, the other of which defines an output node; d. a second broadband interdigitated output transducer having a center frequency less than 10.7 MHz disposed on said substrate at the opposite end of said input transducer spaced apart from said input transducer along the path of propagation of the surface wave of said input transducer, said second output transducer having first and second terminals one of which is connected to circuit ground, the other of which defines an output node; e. rectifying means connected to said output nodes of said first and second transducers; f. filter means connected between each of said output nodes and circuit ground whereby the output signal generated across said output transducers exhibits a frequency response having a portion thereof in the range of 10.7 MHz that is substantially linear and thus operable to detect F.M. signals.
Claim 2
Dependent Claim
256 words
A surface wave frequency discriminator for an F.M. receiver comprising: a. a piezoelectric substrate; b. a broadband bidirectional interdigitated input transducer having a center frequency of 10.7 MHZ disposed on said substrate, said input transducer having first and second terminals for receiving an input signal, one of said terminals connected to circuit ground; c. a first broadband interdigitated output transducer having a center frequency greater than 10.7 MHz disposed on said substrate adjacent one end of said input transducer, spaced apart from said input transducer along the path of propagation of the surface wave generated by said input transducer, said first output transducer having first and second terminals, one of which is connected to circuit ground, the other of which defines an output node; d. a second broadband interdigitated output transducer having a center frequency less than 10.7 MHz disposed on said substrate at the opposite end of said input transducer spaced apart from said input transducer along the path of propagation of the surface wave of said input transducer, said second output transducer having first and second terminals one of which is connected to circuit ground, the other of which defines an output node; e. rectifying means connected to said output nodes of said first and second transducers; f. filter means connected between each of said output nodes and circuit ground whereby the output signal generated across said output transducers exhibits a frequency response having a portion thereof in the range of 10.7 MHz that is substantially linear and thus operable to detect F.M. signals.
Claim 3
Dependent Claim
17 words
A surface wave frequency discriminator as set forth in claim 1 wherein said substrate is lithium niobate.
Claim 4
Dependent Claim
37 words
A surface wave frequency discriminator as set forth in claim 1 wherein said first output transducer has a center frequency of about 11.0 MHz and said second output transducer has a center frequency of about 10.4 MHz.
Claim 5
Dependent Claim
59 words
A surface wave discriminator as set forth in claim 1, wherein the electrodes of said input transducer are defined in a preselected pattern to effect a weighting function substantially corresponding to a (sin x)/x function, and the electrodes of said output transducers are defined in a preselected pattern to effect a weighting function substantially corresponding to a (sin2x)x2 function.
Claim 6
Dependent Claim
195 words
A surface wave frequency discriminator having a fractional bandwidth of up to 40 percent comprising: a. a piezoelectric substrate; b. a first broadband interdigitated input transducer having a center frequency slightly higher than the desired center frequency disposed on said substrate to define a first acoustical channel; c. a second broadband interdigitated input transducer having a center frequency slightly lower than the desired center frequency disposed on said substrate to define a second acoustical channel essentially parallel to said first acoustical channel; d. a first output interdigitated transducer having a center frequency slightly higher than the desired center frequency, said first output transducer being disposed on said substrate within said first acoustical channel; e. a second output interdigitated transducer having a center frequency slightly lower than the desired center frequency, said second output transducer being disposed on said substrate wIthin said second acoustical channel; f. rectifying means connected to each of said output transducers; and g. filter means operably connected to each of said output transducers whereby in response to an input signal an output signal is produced across said output transducers having a linear portion defining a fractional bandwidth of up to 40 percent.
Claim 7
Dependent Claim
195 words
A surface wave frequency discriminator having a fractional bandwidth of up to 40 percent comprising: a. a piezoelectric substrate; b. a first broadband interdigitated input transducer having a center frequency slightly higher than the desired center frequency disposed on said substrate to define a first acoustical channel; c. a second broadband interdigitated input transducer having a center frequency slightly lower than the desired center frequency disposed on said substrate to define a second acoustical channel essentially parallel to said first acoustical channel; d. a first output interdigitated transducer having a center frequency slightly higher than the desired center frequency, said first output transducer being disposed on said substrate within said first acoustical channel; e. a second output interdigitated transducer having a center frequency slightly lower than the desired center frequency, said second output transducer being disposed on said substrate wIthin said second acoustical channel; f. rectifying means connected to each of said output transducers; and g. filter means operably connected to each of said output transducers whereby in response to an input signal an output signal is produced across said output transducers having a linear portion defining a fractional bandwidth of up to 40 percent.
Claim 8
Dependent Claim
30 words
A surface wave frequency discriminator as set forth in claim 5 wherein said first acoustical channel and said second acoustical channel are formed on opposite sides of the same substrate.
Claim 9
Dependent Claim
177 words
A frequency discriminator comprising in combination on a piezoelectric substrate; a. an input interdigital acoustic surface wave transducer having a preselected center frequency and defining an acoustic channel in said substrate, said input transducer effective to generate an acoustic surface wave in said acoustic channel responsive to a frequency modulated input signal; b. first and second output interdigital acoustic surface wave transducers disposed on said substrate within said acoustic channel, said output transducers respectively effective to produce output signals corresponding to said frequency modulated input signal, said first output transducer characterized by an electrode pattern which defines a center frequency that is higher than said preselected center frequency, said second output transducer characterized by an electrode pattern which defines a center frequency that is lower than said preselected center frequency; and c. rectifying and filtering means for receiving said output signals and providing a dc signal having an amplitude which varies substantially linearally as a function of frequency over a relatively broad frequency range and which has a zero dc amplitude level associated with said center frequency.
Claim 10
Dependent Claim
177 words
A frequency discriminator comprising in combination on a piezoelectric substrate; a. an input interdigital acoustic surface wave transducer having a preselected center frequency and defining an acoustic channel in said substrate, said input transducer effective to generate an acoustic surface wave in said acoustic channel responsive to a frequency modulated input signal; b. first and second output interdigital acoustic surface wave transducers disposed on said substrate within said acoustic channel, said output transducers respectively effective to produce output signals corresponding to said frequency modulated input signal, said first output transducer characterized by an electrode pattern which defines a center frequency that is higher than said preselected center frequency, said second output transducer characterized by an electrode pattern which defines a center frequency that is lower than said preselected center frequency; and c. rectifying and filtering means for receiving said output signals and providing a dc signal having an amplitude which varies substantially linearally as a function of frequency over a relatively broad frequency range and which has a zero dc amplitude level associated with said center frequency.
Claim 11
Dependent Claim
70 words
A surface wave frequency discriminator as set forth in claim 7 wherein electrical tuning means are provided for said input transducer, said tuning means comprising an inductor connected intermediate said input transducer and the input signal, said inductor being shunted to ground by a capacitor, said tuning means being operable to reduce insertion losses by matching the input impedance of said discriminator to the impedance of the input signal source.
Claim 12
Dependent Claim
18 words
A frequency discriminator as set forth in claim 8 wherein said rectifying means comprises a voltage doubler circuit.
Claim 13
Dependent Claim
192 words
A surface wave frequency discriminator comprising: a. a piezoelectric substrate; b. an input interdigital surface wave transducer disposed on said substrate and defining an acoustic channel along the surface thereof, said input transducer having an electrode pattern which defines a preselected center frequency, said input transducer effective to generate an acoustic surface wave responsive to a frequency modulated input signal applied to the electrodes thereof; c. first and second output interdigitated surface wave transducers disposed on opposite sides of said input transducer within said acoustic channel and effective to generate electrical signals upon interaction with said acoustic surface wave, said first output transducer characterized by an electrode pattern which defines a center frequency that is higher than said preselected center frequency, said second output transducer characterized by an electrode pattern which defines a center frequency that is lower than said preselected center frequency; and d. coupling means connecting said pair of output transducers to a load, said coupling means effective to rectify the electrical signals generated by said output transducers to produce a dc signal having an amplitude which varies substantially linearly as a function of frequency over a predetermined frequency range.
Claim 14
Dependent Claim
192 words
A surface wave frequency discriminator comprising: a. a piezoelectric substrate; b. an input interdigital surface wave transducer disposed on said substrate and defining an acoustic channel along the surface thereof, said input transducer having an electrode pattern which defines a preselected center frequency, said input transducer effective to generate an acoustic surface wave responsive to a frequency modulated input signal applied to the electrodes thereof; c. first and second output interdigitated surface wave transducers disposed on opposite sides of said input transducer within said acoustic channel and effective to generate electrical signals upon interaction with said acoustic surface wave, said first output transducer characterized by an electrode pattern which defines a center frequency that is higher than said preselected center frequency, said second output transducer characterized by an electrode pattern which defines a center frequency that is lower than said preselected center frequency; and d. coupling means connecting said pair of output transducers to a load, said coupling means effective to rectify the electrical signals generated by said output transducers to produce a dc signal having an amplitude which varies substantially linearly as a function of frequency over a predetermined frequency range.
Claim 15
Dependent Claim
32 words
A surface wave frequency discriminator as set forth in claim 10 wherein said input transducer is unidirectional, radiating relatively low frequencies in one direction and relatively high frequencies in the opposite direction.
Claim 16
Dependent Claim
17 words
A surface wave frequency dIscriminator as set forth in claim 11 wherein said output transducers are unidirectional.
Claim 17
Dependent Claim
51 words
A surface wave frequency discriminator as set forth in claim 10 wherein said coupling means further include filter means connected in series with the output of each of said output transducers, said filter means comprising an R-C circuit operably to filter the r.f. component from the output of said output transducers.
Claim 18
Dependent Claim
18 words
A surface wave frequency discriminator as set forth in claim 10 wherein said coupling means comprise an inductor.
Claim 19
Dependent Claim
211 words
In a system for detecting a frequency modulated signal which includes means for receiving and selecting a frequency modulated signal, means for amplifying and limiting the signal, a discriminator means for converting the frequency modulated signal into audio frequency variations of different amplitude, and audio amplifier and reproduction means for converting the electrical signal into audible sound, the improvement wherein said discriminator means comprises: a. an input interdigital acoustic surface wave transducer defined on a piezoelectric substrate to define an acoustic channel, said input transducer characterized by a preselected center frequency; b. first and second output interdigital acoustic surface wave transducers defined on said substrate within said acoustic channel, at opposite ends of said input transducer, said first output transducer characterized by a center frequency that is greater than said preselected center frequency, and said second output transducer characterized by a center frequency that is less than said preselected center frequency, said first and second output transducers effective to provide output signals corresponding to the frequency of a frequency modulated signal applied to said input transducer; and c. rectifying means for receiving said output signals and providing a dc signal for connection to said audio amplifier, said dc signal having an amplitude which varies substantially linearly as a function of frequency.
Claim 20
Dependent Claim
211 words
In a system for detecting a frequency modulated signal which includes means for receiving and selecting a frequency modulated signal, means for amplifying and limiting the signal, a discriminator means for converting the frequency modulated signal into audio frequency variations of different amplitude, and audio amplifier and reproduction means for converting the electrical signal into audible sound, the improvement wherein said discriminator means comprises: a. an input interdigital acoustic surface wave transducer defined on a piezoelectric substrate to define an acoustic channel, said input transducer characterized by a preselected center frequency; b. first and second output interdigital acoustic surface wave transducers defined on said substrate within said acoustic channel, at opposite ends of said input transducer, said first output transducer characterized by a center frequency that is greater than said preselected center frequency, and said second output transducer characterized by a center frequency that is less than said preselected center frequency, said first and second output transducers effective to provide output signals corresponding to the frequency of a frequency modulated signal applied to said input transducer; and c. rectifying means for receiving said output signals and providing a dc signal for connection to said audio amplifier, said dc signal having an amplitude which varies substantially linearly as a function of frequency.
Claim 21
Dependent Claim
66 words
A system in accordance with claim 15 wherein said discriminator comprises an input transducer the electrodes of which are defined to effect amplitude weighting substantially corresponding to an impulse response defined by a truncated (sin x)/x curve, and a pair of output transducers, the electrodes of which are defined to effect amplitude weighting which substantially corresponds to an impulse response defined by a truncated (sin2x)/(x2) curve.
Claim 22
Dependent Claim
32 words
A system for detecting a frequency modulated signal in accordance with claim 15 further including parallel tuning means operable to match the impedance of the output load and thereby reduce insertion losses.
Claim 23
Dependent Claim
32 words
A system for detecting a frequency modulated signal in accordance with claim 15 further including series tuning means operable to match the impedance of the output lead and thereby reduce insertion losses.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-07-30 | 1977-01-29 | 1977-07-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-30 | 1981-01-29 | 1981-07-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-30 | 1985-01-29 | 1985-07-31 | $7700.00 | Window Closed / Lapsed |